Effect of Mixing on the Particle Size Distribution of Paracetamol Continuous Cooling Crystallization Products Using a Computational Fluid Dynamics–Population Balance Equation Simulation

Abstract

Continuous crystallization is a widely viewed topic as it has many advantages in industrial production. However, it is very resource intensive and time-consuming to determine operation conditions through trial and error. Computer simulation appears to an effective method in continuous crystallization design. The continuous cooling crystallization of paracetamol in a 5 L crystallizer was modeled to investigate the effect of mixing on the particle size distribution (PSD). A novel coupled computational fluid dynamics–population balance equation (CFD–PBE) simulation was developed in which the PBE was discretized using a high-resolution central scheme and solved simultaneously with CFD equations in ANSYS FLUENT 15.0 utilizing user-defined scalars. The influences of both internal grid and external (spatial) grid on the final PSD were studied, and an appropriate grid was chosen. The spatial distribution of velocity, temperature, slurry density, and nucleation rate were simulated. The continuous cooling crystallization under different stirrer speeds, bath temperatures, and residence times was investigated. It was found that (a) higher stirrer speeds lead to uniform distribution but smaller PSD, and (b) as the average temperature gets higher, or the residence time gets longer, the influence of mixing on final PSD gets smaller.